The invention relates to a method of manufacturing a shell element for an electronic device, said shell element having a front and at least one part that is angled in relation to said front, said shell element further comprising a formed sheet that constitutes at least a part of the outer surface of said front and at least a part of said part that is angled in relation to the front of the shell element, said method comprising the steps of:
forming a sheet to a desired shape including a part that is angled in relation to a front part,
injection moulding a plastics material on the back of the formed sheet.
The invention further relates to a shell element manufactured by this method.
The term electronic device includes portable radio communication equipment which includes all equipment such as mobile telephones, pagers, communicators, i.e. electronic organizers, smartphones or the like. Another example of an electronic device is a Personal Digital Assistant (PDA).
In order to produce electronic equipment such as mobile phones with varying outer appearances, a number of different techniques have been developed. One of these techniques is the one described above in which a sheet of e.g. PC (polycarbonate) is provided with a decoration in terms of a print. The sheet is then formed into a desired shape by first heating the sheet, e.g. in an infra-red oven, and then use any conventionally known technique to form the heated sheet, e.g. by high pressure forming, hydro forming or vacuum forming. The heated sheet may also be positioned in a press mould with mould parts that form the sheet into the desired shape.
When the sheet is cooled, it is removed from the press mould or male form part. In relation to the present invention, the formed sheet is provided with at least one partxe2x80x94preferably a circumferential flangexe2x80x94that is angled in relation to the front of the formed sheet.
Usually, the edges of the formed sheet are trimmed and openings for e.g. keys and a display are provided in the front of the formed sheet. The openings may be made by punching or cutting.
The formed sheet is then positioned in an injection mould in which one mould part has an inner shape that is complementary to the outer shape of the formed sheet and of the finished shell element. The mould part is provided with protrusions that extend into the openings of the formed sheet. The protrusions of the mould part abut the other mould part when the injection mould is closed.
A plastics material, such as PC or ABS, is injected into the closed injection mould onto the back of the formed sheet. Due to the above-mentioned protrusions the finished shell element is provided with openings corresponding to the openings in the formed sheet.
When the plastics material is cooled, the finished shell element is removed from the injection mould. The shell element needs no further trimming.
By using the above-described method, varying outer appearances of e.g. mobile phones may be accomplished by varying only the printed decoration on the sheet, i.e. the method of manufacturing remains unchanged. This technique has therefore been found to be economically beneficial if it is desired to vary the outer appearances of a shell element for electronic devices.
JP patent abstract No. 59-152,834 discloses a method of manufacturing a plastics injection moulded item with openings and an injection mould therefore. The injection mould is provided with stamping pins that punch the openings in a preformed and decorated sheet when the injection mould is closed. The plastics material is then injection moulded directly on the back of the preformed sheet to form a finished shell element.
According to the prior art, shell elements of the type described above are manufactured with openings in the front part only. If a component is to be mounted in a part of the shell element that is angled in relation to the front part, this area is provided with a notch extending from the edge, and the component is mounted in the notch. However, this way of mounting a component does not fasten the component satisfactorily to the shell element since, at the one side, the component is not supported by the shell element.
A bore may be provided in the angled area for mounting a component securely. This, however, requires an additional working procedure which further results in more waste from the removed material.
It is an object of the invention to provide a method of manufacturing a shell element of the above-mentioned type in which it is possible to mount a component directly in an opening in an angled area in relation to the front part of the shell element, which method overcomes the above-mentioned problems.
This object is achieved by providing at least one opening in the angled part of the formed sheet mentioned in the opening paragraph, said opening being provided before the plastics material is injection moulded on the back of the formed sheet and leaving the at least one opening open during the injection moulding of a plastics material on the back of the formed sheet.
Thereby the finished shell element is manufactured with an opening in an angled part without need for any further trimming.
The opening in the angled part of the formed sheet is preferably punched or cut out. The punching or cutting of the opening in the angled part may be performed in the same tool and in the same working procedure in which the openings in the front of the formed sheet is punched or cut, or it may be provided in a separate tool.
The edges of the formed sheet are preferably trimmed and openings in the front part of the formed sheet, if any, are preferably provided before the plastics material is injection moulded on the back of the formed sheet. Thereby no further trimming of the finished shell element after injection moulding is necessary.
The injection mould may be provided with at least one raised portion that extends into at least one opening of the formed sheet when the formed sheet is positioned in the injection mould, or it may be provided with at least one displaceable core member that is displaced into at least one opening of the formed sheet when the formed sheet is positioned in the injection mould.
If the injection mould is provided with raised portions, the injection mould can be made relatively simple. This structure requires, however, that the formed sheet as well as the finished shell element is sufficiently flexible in order to flex into and out of the injection mould part that has these raised portions. A more complex structure of the injection mould is achieved if it is provided with displaceable cores. However, if the material used is relatively unflexible, this may be a preferred injection mould structure since the formed sheet can be positioned directly in the injection mould without flexing, and the finished shell element can be removed from the injection mould without flexing.
The formed sheet may preferably cover the entire front of the shell element while the angled part comprises a circumferential flange that extends from the front of the shell element. Thereby the outlook of the shell element is determined solely by the appearance of the formed sheet. The plastics material that is injection moulded onto the back of the formed sheet can therefore be of any kind that fulfils the physical requirements to the material regardless of colour and appearance.
In a preferred embodiment the sheet is a plastics material, such as polycarbonate (PC), and the material that is injection moulded on the back of the formed sheet is also a plastics material, such as PC or ABS. Such plastics materials can be easily formed to the desired shape and are very suitable for injection moulding and calls for good chemical bonding between the formed sheet and the backing.
The electronic device, which the shell element is intended for, is preferably a mobile radio station, such as a mobile telephone.
It shall be emphasised that the term xe2x80x9ccomprise/comprisingxe2x80x9d when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps components or groups thereof.